Green Infrastructure Mitigates the Impact of Urban Flooding

The two major impacts of climate change will be higher rainfalls and temperatures. The impacts of the current East Australian storm event identify shortcomings in the way we have planned our city stormwater infrastructure. Now is the time to adapt our urban planning strategy because the current paradigm fails. Aging stormwater systems in Capital Cities can be aided by green infrastructure. Rooftops represent 28% of urban areas. Rooftops are designed to capture and release stormwater directly to outlets which connect to the suburban network of pipes leading to ocean outfall. A simple engineering solution. Streets, major roads, plazas, footpaths also capture stormwater and directly transfer it to the same networks of pipes. Another simple engineering solution. However the sytem of pipes does not expand exponentially with a growing urban area ie to service more roads, footpaths rooftops etc. The result is urban flooding. Urban hard surfaces are responsible for urban flooding and for the Urban Heat Island effect ie higher city temperatures. Green Infrastructure will mitigate both these impacts but it requires leadership from Governments with new policy, incentives, research grants, training programs and financial investment.

Political leaders point the finger at Nature. It is not Nature; it is a mismanagement of urban stormwater systems and building codes. If houses and beaches are ruined by storm surge it is because the coastal dune systems have been removed. If suburbs are flooded it is because they have been built over natural wetlands. If stormwater pipes become blocked it is because they are inefficient. 

New York was subject to "Sandy' a massive storm surge which infiltrated streets, subways and left the city crippled. The water from the surge had nowhere to drain. As a solution for climate adaption NYC provided grants for green roofs which retain stormwater at the source and implemented rain gardens, street swales to access deep soil connection for water drainage. NYC identified the failures in urban planning and initiated urban solutions.

As the urban area of Australian Capital Cities expand there needs to be a new paradigm of planning. It's referred to as Green Infrastructure which incorporates infiltration pits, swales, rain gardens, urban forests & green roofs planned in conjunction with standard grey infrastructure services. Green provides a plug for stormwater to drain into the natural water table. Grey provides an impermeable layer over the landscape with only an inefficient plug hole that has now become too small. The time for change and adaption is NOW.